Determination of underivatized amino acids to evaluate quality of beer by capillary electrophoresis with online sweeping technique

Abstract

Capillary electrophoresis (CE) with ultraviolet detection was applied to determine underivatized amino acids in beer, based on the coordination interaction of copper ions and amino acids. An online sweeping technique was combined with CE to improve detection sensitivity. Using the United Nations Food Agriculture Organization/World Health Organization model of essential amino acid pattern and flavor of amino acids, the quality and taste in three kinds of beer were evaluated. It was found that Beer2 had higher quality than the other two kinds and the content of phenylalanine, proline, serine, and isoleucine was relatively large in all three kinds of beers with a great influence on beer flavor. Optimal conditions for separation were as follows: 50mM CuSO at pH 4.40 as buffer; total length of fused silica capillary, 73 cm; effective length, 65 cm; separation voltage, 22.5 kV; and optimized sweeping condition, 70 seconds. In the appropriate range, linearity (r > 0.9989), precision with a relative standard deviation < 8.05% (n = 5), limits of detection (0.13-0.25 μg/mL), limit of quantification (0.43-0.83 μg/mL), and recovery (80.5-115.8%) were measured. This method was shown to be applicable to the separation of amino acids in beer and to perform quantitative analysis directly without derivatization for the first time.

Determination of Free Tryptophan in Beer Samples by Capillary Isotachophoretic Method

“…The determination of amino acids in food, including beer samples, has been carried out employing different techniques, while the most popular are as follows: capillary electrophoresis (Cortacero-Ramírez et al 2004;Guo et al 2019;Luo et al 2017;Turkia et al 2015) and liquid chromatography with different detection systems (Liyanaarachchi et al 2018;Moreno-Rojas et al 2018;Palomino-Vasco et al 2019;Poveda 2019;Redruello et al 2017). Recently, micellar electrokinetic chromatography and micellar liquid chromatography were described as alternative method to classical HPLC (Ke et al 2017;Ke et al 2019;Tezcan et al 2013;Yan et al 2014) and applied for beverage samples (Gil-Agustí et al 2007;Huang et al 2019;Xie et al 2018).…”

Direct determination of amino acids in brewery worts produced by different processes by capillary zone electrophoresis

“…Although LOD and LOQ obtained for the AAs were higher than those of the other works previously published, these values were suitable for the purpose of this work. As can be seen in the Supporting Information Table 3, it is noteworthy that there are no method developed for the determination of AAs in the brewery wort samples ; therefore, this is the first time that a CE method is applied in the direct determination (without derivatization reaction) of Cys, His, Phe, Lys, Trp and Arg in brewery worts.…”

“…In addition, the biogenic amines, commonly found in beers, can react with O‐phthalaldehyde and the by‐products can interfere in analysis . Nevertheless, only few papers have described the determination of AAs in beer samples (not worts) by CE without a derivatization step, using UV detection and contactless conductivity detection .…”

Determination of Free Amino Acids in Three Species of Duckweed (Lemnaceae)

“…In general, the FAAs are extracted with solvents water, formic acid, hydrochloric acid, or ethanol, followed by filtration or centrifugation before analysis [15][16][17]. Several techniques have been described for detection of free amino acids including ionexchange chromatography [18], precolumn derivatization followed by reversed high-performance liquid chromatography coupled with diode array or fluorescence detector [19,20], gas chromatography, mass spectrometry, and capillary electrophoresis [21]. In recent years, determination of FAAs using ultrahigh performance liquid chromatography hyphenated to mass spectrometry has gained great notice because of the merit of selective separation for the polar underivatized analytes under HILIC condition with acetonitrile-dominated mobile phase [22][23][24][25].…”